Safety pull bar for paper cutting machines



March 7, 1961 c. THUMIM SAFETY PULL BAR FOR PAPER CUTTING MACHINES Filed July 2, 1957 2 Sheets-Sheet 1 INVENTOR. 64%.! 7/7 U/W/W March 7, 1961 c. THUMIM SAFETY PULL BAR FOR PAPER CUTTING MACHINES 2 Sheets-Sheet 2 Filed July 2, 1957 INVENTOR. JWKA 77/0/40 United States Patent ,0

SAFETY PULL BAR FOR PAPER CUTTING MACHINES Carl Thumim, Westbury, N.Y., assignor, by mesne assignments, to Miehle-G ss-Dexter, Inc., Chicago, 111., a corporation of Delaware (Filed July 2, 1957, Ser. No. 669,608 1 Claim. (Cl. 19 2 -150) Thisinvention relates to paper cutting machines of the type. having a knife bar pulled at both ends by means of respective pull bars for the purpose of drawing the knife through a paper pile.

It is an objectof. the invention to provide a safety mechanism wherein electricmotor power or mechanical power is shut ofi in the'event that tension in the pull bars become excessively great. i

It is' another object of the invention; to provide compact means carried bythe pull bars themselves which shut off through a suitablehcontrol circuit electric curred to an electricallycontrolled clutch or to an electromagnetic chitchthrough which. mechanical power is carried tp the knifepulling mechanism; L"

It is a further object of thetinvention to provide .a simple and wgged switch arrangement in conjunction with pull bars which will trigger a circuit to cut off power to the knife in response to a predetermined tension in the pull bars.

In general, excessive loads occur on the pull bars on the end of a knife stroke due to the small moment arms of the crank pins which operate pull bars in mechanisms where crank pins are utilized for that purpose, for example in my copending application Serial No. 661,534, filed May 24, 1957. Such small moment arms may not be accompanied by sufficient torque in the crank shafts to shear the usual shear pin. Accordingly, the present invention overcomes this problem by providing micro-switches carried by each pull bar in conjunction with a series of flexible spring washers carried coaxially on the bar and through which washers tension on the bar is exerted. The washer arrangement is such that upon a predetermined degree of compression thereof the switch is actuated to trigger a cutoff relay in an associated control circuit wherein the circuit may function either to cut off current to an electrically controlled clutch or to disengage the electromagnetic clutch, etc.

A detailed description of the invention will now be given in conjunction with the appended drawing in which:

Figure 1 is an elevation showing the relationship of a pair of pull bars for drawing the knife bar of a paper cutter. I

Figure 2 is a section through 2-2 of Figure 1.

Figure 3 is a section through 3--3 of Figure 1.

Figure 4 is a magnified view of an end of a pull bar partially in section.

Figure 5 shows a basic circuit for control of an electrically controlled hydraulic clutch or an electromagnetic clutch which circuit is operative in response to the pull bar operated switches.

Referring now to the drawing'and, in particular, to Figure 1, the disposition of a pair of pull bars and is disclosed in the positions they would have when operatively connected in a draw bar knife machine. Thus, the pull bar 10 would connect to one end of the knife bar, while the pull bar 15 would operate a bell crank (not shown) which in turn would pull a link (not shown) for actuation of the other end of the knife bar.

the actuation of the pull bars is disclosed as being effected through crank pins such as 10a and 15a carried by crank arms 1% and 15b, respectively, which are secured to and rotated by crank shafts 10c and 150, respectively. Thus, it will be apparent'that upon rotation of the crank arms 1% and 1511, the ends of the respective pull bars are rotated about the axis of the crank shafts for the purpose of exerting a tension through the bars to draw the knife through a paper pile, all as will be well understoodby persons skilled in the art.

The crank pinend of each pull bar carries a microswitch 20 having a button 20'a actuable by an adjustable bolt member 25 carried in a suitable housing as shown,

all as seen in Figure 2. The microswitch 20 iscarried by a yoke 40 whichis connected to the crankpin', such as crank pin 15 1, said yoke having an end cap 44 secured thereto as by bolts or pins 47, which end cap is apertured to take the turned down end 32a'of a socket member 32 which secures the pull'bar. The-end 32a is slidable within the aperture in the end cap and carries a collar 50 threaded theretoand wherein a set screw 53 is provided to maintain adjusted position between the parts. The collar 50 carries the adjustable bolt 25 which engages the micro switch button 20:1.

The pull bar 1 5 may move axially with respect to yoke member 40, being limited in movement totheleft, as viewed in Figure 4, by theslrould'er abutment. 5'4 and in movementtothe right'by a series of spring washers of dished arrangement consisting for example, of two pairs of washers such as 60. Thus, each pair of washers is associated concave face to concave face and mounted in tandem on the end 32a of the socket member 32. For other loadings, washers may be stacked concave to convex to increase the load at deflection. The present washers are stacked to increase deflections of a given' the pull bar 15 moves axially under tension with respect to the yoke 40, some compression of the washers is effected by virtue of the tension in the pull bar. However, the arrangement is such that due to pre-loading normal tension will not cause the switch actuator bolt 25 to have any axial motion to operate switch button 20a to cut-off position. Where, however, a predetermined degree of tension is met, collar 50 carries bolt 25 to a sufficient degree in engagement with button 20a of the switch mounted on yoke 40 to actuate the switch to make or break contact, depending on the type of switch employed.

By means of a suitable electrical control circuit, as

shown in Figure 5, it will be understood that rotary power to the knife is cut-ofi on overload of either pull bar, a normally closed switch being used in this instance. Opening of the micro-switch (one or both) in the overload coupling will drop out the clutch control current and the CR-8 lock-out relay. The knife will immediately stop and cannot be restarted until the two hand switches are released and then engaged.

The wiring functions as follows:

When the push button switch 5-6 is released it energizes relay CR-S, thereby closing contacts CR-8 and holding the relay energized continuously even if the push button is actuated. To operate the cutting, the push button is pressed closing contacts 89 to energize the clamp valve solenoid and allowing the clamp to go down. Attached to this solenoid is clamp valve contacts 8-10 which closes the knife relay, which in turn energizes the clutch through circuits not shown. This clutch may be either of the electro-magnetic type or the electro-hydraulic type. On its return stroke, the knife crank operated cam PatentedMar. 7, 1961 opens cam limit switch 7--2 de-energizing the whole circuit stopping the knife and allowing the clamp to come up. This happens even though the push button is held down. For another operation, the push button must be released to reset relay CR-8 and then pushed to start the cycle. The overload micro-switches *12and 34 attached to the 2 pull rods will interupt the whole circuit at any time an overload is encountered. The push button then would have to be released to reset CR-8 pushed again to continue the cycle. Before the last operation the overload should be removed.

It will be apparent that collar 50 may be taken up on threaded end 32a to provide any degree of initial compression in the washers 60 so as to predetermine the amount of tension required to operate the microswitch. Likewise, the extent of relative motion between the pull bar and the yoke before actuation of the microswitch is effected may be adjusted by means of the bolt 25 and jam nut 25a.

Having thus described my invention, I am aware that various changes may be made without departing from the spirit thereof, and accordingly I do not seek to be limited to the precise illustration herein given except as set forth in the appended claim.

I claim:

In a device of the class described, a pull bar for one end of a paper cutting knife comprising an elongated tensile bar member, a connector member at the end of said bar member for connecting said bar member to an electro-mechanical source of power to exert a pull through said bar, resilient means intermediate said pull bar member and said connector member to provide relative motion between said bar and said connector member upon predetermined tension being exerted through said bar member, and switch means carried by said members comprising a switch actuable upon a predetermined degree of relative motion between said members, including a control circuit operated by said switch to'render said source of power ineflective to pull said bar upon actuation of said switch, said connector member comprising a yoke disposed at the end of said pull bar member and having an aperture through which an integral portion of said pull bar slidably extends, said portion having a threaded end, said resilient means being carried on said threaded end, an adjusting collar carried on said threaded end for in itially compressing said resilient means, said resilient means being disposed to transmit tension between said yoke and said adjusting collar, said yoke having means for connection to a crank, said switch means comprising a push button micro-switch carried by one of said members, and a switch actuator carried by the other of said members, and comprising an actuator element having means to independently adjust relative to said one member to selected positions in the direction of motion to ward said push button micro-switch.

References Cited in the file of this patent UNITED STATES PATENTS 1,386,559 Fegely Aug. 2, 1921 1,814,732 Nyborg et a1 July 14, 1931 1,892,069 Miller Dec. 27, 1932 2,130,764 Conklin Sept. 20, 1938 2,340,465 Gerlach Feb. 1, 1944 2,407,537 Chapman Sept. 20, 1946 2,483,730 Lake et a1. NOV. 22, 1949 2,685,873 Cooke Aug. 10, 1954 

